Cell phone muting override system

ABSTRACT

The disclosed invention relates to a system for restricting radio frequency transmissions within a restricted area and more particularly to a mechanism for overriding the restriction of radio frequency transmissions within a restricted area using an override mechanism. A restricted area is defined wherein all radio frequency transmissions are restricted. Within the restricted a plurality of cellular telephones is disposed, each with a radio frequency transmitter and a radio frequency receiver. An emergency override is also disposed within the restricted area, the emergency override capable of selectively enabling communications of a selected subset of the cellular telephones disposed within the restricted area.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/687,024, filed Oct. 16, 2003 now U.S. Pat. No. 7,142,877, which is acontinuation of U.S. patent application Ser. No. 09/384,723, filed Aug.27, 1999, now U.S. Pat. No. 6,675,002.

FIELD OF THE INVENTION

This invention is in the field of automatically muting electronicdevices that emit sound or radio frequency signals, where muting meansinhibiting generation or reproduction of objectionable electronic soundor radio-signals, or reducing such sound or radio-signals to anacceptable level.

DESCRIPTION OF THE PRIOR ART

People attending a concert, or similar event, are distracted andirritated when cellular telephones and pagers ring. During a quiet anddelicate passage, a musician can be distracted by a ringing cell phone,stopping the performance. Attendees at churches, synagogues, lecturehalls, and even restaurants are similarly distracted by cellulartelephones, pagers, wrist watches, and other electronic devices thatreproduce or generate audio signals. Cell phones should not be used inairplanes. However, individuals do not have the courtesy to turn thesedevices off, or at least, mute them, when they might distract others orinterfere with navigation.

Nevertheless, it is possible to automatically mute these devices bymaking a signal present in the concert hall, or similar area (restrictedarea), or through entrances or exits to these areas, which can bereceived by the offending device (restricted device). This inventiveapparatus will automatically mute all restricted devices in restrictedareas, provided that restricted areas, or entrances to, and possiblyexits from, the areas are equipped with a transmitter apparatus, and allrestricted devices are fitted with a receiver apparatus, according tothis invention.

OBJECTS OF THE INVENTION

Accordingly, it is an objective of this invention to disable theoperation of a cellular telephone or other mobile communications devicein the vicinity of “high value” areas.

SUMMARY OF THE INVENTION

Accordingly, the disclosed invention relates to a system for restrictingradio frequency transmissions within a restricted area including amechanism for overriding the restriction of radio frequencytransmissions within the restricted area. Through some means, arestricted area is defined wherein all radio frequency transmissions arerestricted. A cellular telephone is disposed within the restricted area,the cellular telephone including a radio frequency transmitter and aradio frequency receiver. An emergency override mechanism is alsodisposed within the restricted area, the emergency override capable ofselectively enabling communications of a selected subset of the cellulartelephones disposed within the restricted area.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the present invention which are believed to be novel areset forth with particularity in the appended claims. The invention,together with the further objects and advantages thereof, may best beunderstood by reference to the following description taken inconjunction with the accompanying drawings, in the several figures ofwhich like reference numerals identify like elements, and in which:

FIG. 1 is a top plan view of the general organization of the systemconstructed in accordance with the general principles of the presentinvention.

FIG. 2 is a description of a control signal sent from transmitter toreceiver.

FIG. 3 is a description of a layout of multiple transmitters to cover alarge restricted area.

FIG. 4 is a preferred embodiment design of a transmitter.

FIG. 5 is a C language declaration of ports used in FIG. 6 and FIG. 8.

FIG. 6 is a pair of C language procedures executed in the transmitter.

FIG. 7 is a preferred embodiment design of a receiver.

FIG. 8 is a pair of C language procedures executed in the receiver.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT

A high-level view of the operation of this apparatus is presented first.Then a concrete design of a preferred embodiment is presented later.

FIG. 1 illustrates the general organization of this apparatus. Arestricted area 103 may be protected by one of three operating modes ora combination thereof. In a first mode, the restricted area has one ormore control signal transmitters 100, and one or more restricted devices101 may be carried by persons in the area. The control signal 102 passesthroughout (blankets) the restricted area 103. Whenever restricteddevice 101 receives the control signal 102, it will be muted.Alternatively in a second operating mode, a first control signaltransmitter 105 may be placed by each entrance 104 to a restricted area103, and a second control signal transmitter 106 may be placed by eachexit 107 from a restricted area 103. When a restricted device 101receives a control signal from first control signal transmitter 105, itis muted until the restricted device 101 receives a control signal fromsecond control signal transmitter 106. In a variation of this mode, forinstance in an airport jetway, a second control signal is emitted nearthe airport terminus of the jetway, and the first control signal isemitted near the airplane terminus of the jetway. As a restricted devicepasses through the jetway into an airplane, the last-met signal mutesthe device before it enters the airplane, and as a restricted devicepasses through the jetway out of an airplane, the last-met signalrestores the device to the non-muted state before it enters the airport.Finally, in a third operating mode, a control signal transmitter 105 maybe placed by each entrance 104 to a restricted area 103. Upon receipt ofa control signal from control signal transmitter 105, a restricteddevice 101 is muted for a period of time, such as three hours.

In this preferred embodiment, essentially the same hardware is used forall three modes to reduce cost. The preferred control signal isultrasound, because in an area-blanketing mode, this signal should haveradiation coverage that is similar to the objectionable sound that itmutes, but must not be objectionable itself. But without departing fromthe spirit of this invention, any combination of the aforementionedmodes may be implemented, each mode may use different hardware, or thecontrol signal can be a limited-range radio wave, infrared signal, orother local signal that can broadcast over the entire restricted area,possibly by using multiple transmitters in the restricted area, and notbroadcast significantly, or be present coincidentally, beyond this area.

The ultrasonic signal should be an unusual pattern of ultrasonic bursts.Otherwise devices like ultrasonic pest deterrents and ultrasonicdistance measurement devices, which emit continuous ultrasonic energy,or simple repetitions of ultrasonic energy, might be used innonrestrictive areas. Such ultrasonic transmitters should notaccidentally mute restricted devices. Restricted electronic devices aregenerally controlled by microcontrollers. Most microcontrollers have atleast one UART (Universal Asynchronous Receiver-Transmitter (orequivalent) module), or if not, many such UART modules are alreadydesigned and can be inexpensively included in the design of a specialmicrocontroller used in restricted devices. Therefore the ultrasonicsignal should be modulated by a communication frame (or packet) signalthat is sent and that will be received by UARTs. This preferredembodiment will utilize three UART frames sent at 600 baud, having noparity bit and one stop bit, which (1) have binary pattern 10001101 orhexadecimal pattern in C notation, 0x8d (FIG. 2 shows such a signal atoutput RxD 123 in FIG. 4), (2) have binary pattern 10101110 orhexadecimal pattern 0xae, or (3) have binary pattern 11100110 orhexadecimal pattern 0xe6; each frame has a variation of single bit-widepulses, and multiple bit-wide pulses, which is unlikely to appear inpatterns generated by naturally occurring sources or in use for othercommunication or control applications. However, another communicationframe structure, or a signal not presently used for communication, canbe used without departing from the spirit of this invention.

The following discussion pertains mainly to area blanketing transmitters100. A pattern frame from transmitter 100 should be sent repetitively,but no signal should be sent for multiple frame times, so that if aplurality of transmitters are needed to cover a restricted area,different transmitters can transmit their frame at different timeswithout interfering with other transmitters. This should be done so thata restricted device will receive a frame from at least one of thetransmitters without interference from another transmitter that mightcancel the signal. Further, if a signal is sent from a transmitter, andif interference from a reflected signal from the same transmittercancels its signal, the restricted device should be able to receive aframe from another transmitter without it being cancelled. In thispreferred embodiment, a frame is sent every four frame times by onetransmitter. If a large number of transmitters are needed to cover arestricted area, transmitters can be arranged in a repetitivetwo-dimensional array pattern as shown in FIG. 3, where for purposes ofdescription, transmitters are arranged in rows numbered consecutivelyfrom top to bottom, and in columns numbered consecutively from left toright. The transmitters will be synchronized to insure that anyrestricted device in the restricted area will receive at least onesignal without cancellation by a signal sent by another transmitter.Each transmitter will send its frame in a time slot, and repeated eachfour time slots after that. A transmitter (110 a, 110 b, . . . ) in aneven numbered row and even numbered column will send its frame in aframe time slot zero. A transmitter (111 a, 111 b, . . . ) in an evennumbered row and odd numbered column will send its frame in a frame timeslot one. A transmitter (112 a, 112 b, . . . ) in an odd numbered rowand even numbered column will send its frame in a frame time slot two. Atransmitter (113 a, 113 b, . . . ) in an odd numbered row and oddnumbered column will send its frame in a frame time slot three. In therestricted area, any restricted device, receiving a signal from twodifferent transmitters that might interfere with each other, willreceive a signal from some other transmitter. This transmitter will bemuch closer to the receiver than any other transmitter that is sending asignal in the same frame time slot. Thus, a restricted device willreceive a frame from at least one transmitter, without risk ofcancellation by a signal from another transmitter. A control signalreceived from any transmitter will mute the restricted device for a timethat is at least as long as the time between signals from thattransmitter, which is four time slots in this preferred embodiment. Whenthe restricted device is removed from the restricted area, it will notreceive the control signal, and will not be muted. Use of anotherperiodic frame structure, other than sending a frame every four frametimes, does not significantly depart from the spirit of this invention.Sending frames in nonrepetitive manner which are not synchronized witheach other, such as sending frames at random times but with apredetermined maximum time between frames, does not significantly departfrom the spirit of this invention.

The following discussion pertains to transmitters at entrances 105 andtransmitters at exits 106. These transmitters should generate distinctframe patterns that are different from the frame pattern 0x8d chosen forarea-blanketing transmitters 100. The frame pattern 0xae is generated byentrance transmitters 105 and the frame pattern 0xe6 is generated byexit transmitters 105. Upon receipt of an entrance frame pattern 0xae,the receiver will be muted, until an exit frame pattern 0xec isreceived. However the exit transmitter 106 might be inoperable or theelectronic device 101 might be taken out of the restricted area withoutpassing through an exit. In this case, the device 101 may beautomatically restored to its non-muted state after a period of time,such as three hours, after it has been muted by an entrance framepattern 0xae. In fact, if the device 101 is automatically restored toits non-muted state after a period of time, and that period of time ispredetermined and is deemed acceptable for the event taking place in therestricted area, an exit signal may not be needed. However, a differentperiod of time than three hours, or the absence of a timeout period, ora period of time that is selectable by sending different entrance framepatterns, can be used without departing from the spirit of thisinvention. Moreover, there being two to the power eight, 256, differentframe patterns, only a few of which might be generated by pestdeterrents and other devices used in nonrestricted areas so they shouldnot be used in this apparatus, many different frame patterns can betransmitted by entrance transmitters 105 to selectively mute eitherradio-frequency generation or audio generation or both, and toselectively mute for various time periods such as ten minutes, twentyminutes, half an hour, and so on, until the device returns automaticallyto a non-muted state, or muted indefinitely, until an exit signalreturns the device to a non-muted state.

A preferred embodiment design of an area-blanketing transmitter (100) isshown in FIG. 4. Microcontroller 120 may be an inexpensive low-powermicrocontroller designed for battery use, such as the Motorola MMC2001.For the detailed preferred embodiment following in this specification,the Motorola MMC2001 Reference Manual (MMC2001RM/D) is incorporated byreference. Parallel port EPDR bit 0121 inputs a signal derived fromhousehold 110 volt 60 Hertz signal that is used to time the transmissionof the control signal, and parallel port EPDR bit 1122 inputs a signalfrom a connector that can be used to synchronize the signal to be sentin a selected frame time. Serial port TxD0 is connected to a NOR gate124 whose other input is the output of 555 timer chip 125 that generatesa 40 KHz wave form. Output of NOR gate 124 is connected to an amplifier126 that drives an ultrasonic transducer 127. When UART signal 123 islow, NOR gate 124 outputs a high signal, and transducer 127 generates a40 KHz ultrasonic signal.

The C language declarations in FIG. 5 are included in the program for anarea-blanketing transmitter (FIG. 6) and in the program for a receiver(FIG. 8). The first statement 129 indicates the location of I/O ports inthe MMC2001; for instance the first declaration indicates a 16-bit portcalled EPDDR at location 0x10007002. The second statement 130 indicatesconstant values that may be combined and stored in I/O ports; forinstance the first definition UART_EN=1 indicates a symbolic nameUART_EN will have a value of 1.

C language procedures for the area-blanketing transmitter are shown inFIG. 5. Procedure init( ) 131 is executed just after the microcontrolleris reset, to configure the I/O devices. Line 132, and the following fourlines, initialize UART0 for 600 Baud transmission of 8-bit data frameswith no parity and one stop bit (assuming the MMC2001 has a 32 MHz clockrate). Line 133 initializes the edge port to recognize rising edgesignals on edge port pins. Procedure put( ) 134 is executed at leastonce every 60th of a second, but can be executed more often in a loop ifthe remaining programs running in the microcontroller execute a loop inless than a 60th of a second. A rising edge of the 60 Hz square wavesets bit zero of port EPFR. Line 135 causes the procedure to return tothe calling program if an edge did not occur. Line 136 clears the bitsin EPFR that had been set to 1. To cause a transmitter to synchronize tothe current 60 Hz period, a pulse is applied via a connector to bit 1 ofthe EPFR device, setting it. If bit 1 of EPFR was set when bit zerobecame set, then the static local variable COUNT is cleared. COUNT isincremented; if COUNT is an integer multiple of four, the pattern 0x8dis written into the UART transmit register, causing pattern 0x8d (FIG.2) to be sent out 137. Thus, a transmitter 100 broadcasts anarea-blanketing signal once every four periods of a 60 Hz waveform, andeach frame, having 8 data, no parity, and one stop bits at 600 baud, isequal to a 60 Hz period, so it does not interfere with a frame sent byanother transmitter that is close to it.

A transmitter for an entrance 105 or a transmitter for an exit 106 canbe implemented in similar manner to that described above. It need not besynchronized to other transmitters, however, and it may emit its framepattern continuously, such that after one frame ends the same frame issent again. By implementing transmitters for area-blanketing, entranceand exit, using the same microcontroller, a single device, suitablyconfigured, can be used for each use. Indeed, a device first configuredfor an entrance can later be configured for an exit when an event isover.

A preferred embodiment design of a receiver and its connections torestricted device 101 is shown in FIG. 6. Microcontroller 140 may be aninexpensive low-power microcontroller such as the aforementionedMotorola MMC2001. Signal output of ultrasonic transducer 141 isamplified, filtered, and detected by analog hardware 142 which sends adigital signal to serial input port RxD0, 143. When a 40 KHz ultrasonicwave is detected by transducer 141 analog hardware 142 outputs a lowdigital signal. Parallel port EPDR bit 0 (144) outputs a signal which isapplied to the sound generating or reproducing device 101 to mute it;when this signal is high, sound output is muted.

Unfortunately, a restricted device may completely be turned off when itis passed through an entrance or an exit, thereby making it unable toreceive and process entrance and exit frames. However, microcontrollerssuch as the Motorola MMC2001 have low-power stop and doze modes, wherebythe microcontroller, though turned off to conserve battery power, can beput in the run mode upon receipt of a signal such as the output ofanalog hardware 142. The microcontroller would be maintained in a stopor doze mode. Then it can be put into a run mode upon receipt of asignal from analog hardware 142 to respond to entrance and exit frames.

C language procedures for the receiver are shown in FIG. 8. Procedureinito 150 is executed just after the microcontroller is reset, toconfigure the I/O devices. Line 151, and the following four lines,initialize UART0 for 600 baud reception of 8-bit data frames with noparity and one stop bit (assuming the MMC2001 has a 32 MHz clock rate).Line 152 initializes the edge port to output a muting signal on edgeport bit 0. Procedure check( ) 153 is executed slightly less often thanevery 15th of a second. UART frames that arrive in the meantime arestored in a hardware queue; each frame's data is read from this queue byreading a byte from port U0TX. Line 154 checks for the presence of aframe's data in the hardware queue. As long as there is data in thequeue, line 155 reads the data. If the frame was received in error,nothing is done (line 155), otherwise if the area blanketing frame 0x8dis received, local variable i is set equal to 1 (line 156) to mute theelectronic device, otherwise if the entrance frame 0xae is received,global variable timeout is set equal to constant N (157) to mute theelectronic device for the next three hours, otherwise if the exit frame0xe6 is received, global variable timeout is cleared (line 158) torestore the electronic device to its non-muted state. If timeout isnonzero, local variable i is set to 1 (line 160) to mute the electronicdevice. Local variable i is output into port EPDR, where a value of 1mutes the restricted device (line 161). The variable timeout isperiodically decremented. (The program segment for this periodicdecrement function is not shown, there being several ways to do this,which are not important to this invention.) The value N (159) isselected such that, unless timeout is prematurely cleared, timeout willbecome zero in a predetermined time, which is three hours in thispreferred embodiment. Thus, if any frame is received without error,having a pattern 0x8d that is sent by area-blanketing transmitter 100,the mute signal is asserted and the objectionable audio signal is notproduced, and if any frame is received without error, having entrancepattern 0xae sent by transmitter 105, the mute signal is asserted andthe objectionable audio signal is not produced for the next three hours,or until exit pattern 0xe6 is received.

Occasionally a need may arise to override the automatic mute control,for instance to permit an emergency telephone signal to ring the cellphone even though it is muted, or for instance to restore a device thatis accidentally muted. However, overriding should not be so easy as todefeat the objective of this invention. A command should be able to besent from a controlled source, such as a service department's telephonehot line, to override the mute control. Request authorization tooverride the muting capability should be administered by the servicedepartment so as to prevent users from flagrantly disabling the mutingcapability, yet handle valid exceptions to automatic control. Acommunication channel will send the command from the service center tothe electronic device. In this preferred embodiment, a command may besent on a cell phone channel. This message can be carried by a signalthat is modulated using frequency-shift keying, which is also used inmodems and faxes. The signal will be modulated using a UART framestructure, for reasons discussed earlier in this specification. Hardwareand software for this preferred embodiment is similar to that forreceiving control signals in a restricted device, as in FIG. 8. whereasthe control signal receiver user UART device numbered zero, there is asecond UART device, numbered one, with the same functionality as UARTdevice numbered zero, that can be coupled through a modem device ofknown design to the cell phone's audio channel. So, in the interests ofbrevity, this hardware and software will not be further described inthis specification. In order to make unauthorized generation orduplication of these commands somewhat more difficult, the electronicdevice's phone number and the current time will be sent in the commands,to prevent one command from disabling many devices or from beingrepeatedly used to disable the same device (the time sent in the commandcan be compared to the current time, which is maintained in most cellphones). At least a simple encryption technique will be used to makeconstruction of these messages more difficult, such as appending a checksum to the end of the message which is the sum of all the bytes in themessage. This can be used to foil counterfeiters of commands who areunskilled in the art of communication protocols. However, withoutdeparting from the spirit of this invention, any communication channelsuch as a regular telephone line or a pager channel can be used; thecommand may be sent on different carriers than frequency-shift keying,such as amplitude modulation; the command may be modulated usingdifferent communication frame structures; the command may be composedusing different frame sequences; and the command may be secured usingmore powerful encryption techniques.

Two mechanisms may be used to restrict the use of control signaltransmitters. In a first mechanism, a command may likewise be able to besent from a controlled source, such as a service department's telephonehot line, through a communication channel to enable and configure atransmitter of control signals. Authorization to enable and configure asignal transmitter should be administered by the service department soas to limit the risk that a transmitter apparatus might be usedmischievously or maliciously. In this preferred embodiment, a commandmay be sent on a telephone channel, carried by a signal that ismodulated using frequency-shift keying, modulated using a UART framestructure, for reasons discussed earlier in this specification. Again,hardware and software for this preferred embodiment is similar to thatfor receiving control signals in a restricted device, as in FIG. 8. So,in the interests of brevity, it will not be further described in thisspecification. The command will contain a signal byte which will betransmitted by the transmitter receiving the command. In order to makeunauthorized generation or duplication of these commands a bit harder,the transmitter should have a unique computer-readable serial number;the command will have this serial number and the current time, toprevent one command from being used to enable and configure otherunauthorized transmitters or from being repeatedly used to enable thesame transmitter, because the time can be compared to the current timethat can be maintained in the transmitter. At least a simple encryptiontechnique will be used to make construction of these commands moredifficult, such as appending a check sum to the end of the message whichis the sum of all the bytes in the message. This can be used to foilcounterfeiters of commands who are unskilled in the art of communicationprotocols. However, without departing from the spirit of this invention,any communication channel such as a cell telephone line or a pagerchannel can be used; the command may be sent on different carriers thanfrequency-shift keying, such as amplitude modulation; the command may bemodulated using different communication frame structures; the commandmay be composed using different sequences of frames, such as containinga range of serial numbers and a range of times, instead of a singleserial number and a single time for which a command is valid; and thecommand may be secured using more powerful encryption techniques.

Alternatively, in a second mechanism, the transmitter can be enabled andconfigured by plugging into it a small cartridge, containing a removablenon-volatile memory such as an electrically erasable programmableread-only memory (EEPROM). Such a cartridge has been commonly used toload games into personal computers or game players, and is similar to a“smart card” or magnetically recorded credit card. The techniques forprogramming such a non-volatile memory, and for connecting such anon-volatile memory to a transmitter device, are well-known to oneskilled in the art. In this alternative preferred embodiment, a servicedepartment will write the EEPROM and mail it to the transmitter's user.Authorization to enable and configure a signal transmitter should beadministered by the service department so as to limit the risk that atransmitter apparatus might be used mischievously or maliciously. TheEEPROM will be read by the transmitter to enable and configure itscontrol signals. The EEPROM will store a signal byte which will betransmitted by the control signal transmitter reading the EEPROM. Inorder to make unauthorized generation or duplication of these commands abit harder, the transmitter should have a unique computer-readableserial number; the EEPROM will store this serial number and the currenttime, to prevent one EEPROM from being used to enable and configureother unauthorized transmitters or from being repeatedly used to enablethe same transmitter, because the time can be compared to the currenttime that can be maintained in the transmitter. At least a simpleencryption technique will be used to make construction of these EEPROMsmore difficult, such as appending a check sum to the end of the messagewhich is the sum of all the bytes in the message. This can be used tofoil counterfeiters of commands who are unskilled in the art ofconstruction of data records. However, without departing from the spiritof this invention, a read-only memory (ROM), a magnetic stripe, oralternative nonvolatile memory may be used in place of an EEPROM, theformat of data in the card might be modified to contain, for instance, aseries of dates and a range of serial numbers, for which authorizationis given, and a more elaborate encryption code can be used.

An important aspect of this invention is its low cost. A restricteddevice can be modified by the modification of a cell phone mouthpiece toalso receive the ultrasonic signals, or else by the addition of anultrasonic transducer. Analog circuitry is also needed to amplify,filter, and detect the ultrasonic signal. The UART hardware may be onthe microcontroller already, or can be added at low cost because UARTdesigns are widely reproduced. The restricted device microcontroller'sprogram need not be greatly expanded. Thus the hardware and softwareneeded to implement this valuable function in receivers will not beexpensive. Also, transmitters will similarly be inexpensive.

As opposed to a radio-interference device, this inventive apparatus doesnot jam a radio-frequency signal carrier. Unidirectional orbidirectional radio transmission may be still permitted, whileobjectionable audible or radio-frequency output is muted. As opposed toinfrared remote controls, which mute television sets and similar homeentertainment devices, this inventive apparatus broadcasts the same mutecontrol signal from possibly more than one transmitter to all receivers.By contrast, infrared remote controls for T.V.s and stereos aredesigned, as much as possible, to control just one device from onetransmitter, such that other devices ignore the control. Finally, thisinventive device solves an onerous problem, as restricted devices arewidely used and are expected to become even more widely used, which noother known apparatus attempts to solve.

Modifications to this invention can be made by one skilled in the artwithout departing from the spirit of the invention. Instead of sendingthe objectionable audio signal, while the signal is muted, an optionalpart of the apparatus can include automatic means to store the messagebeing sent, as in voice-mail, or to inform the sender, by means of aspecial tone or sequence of tones, that the receiver is in a restrictedarea and cannot hear the sound. Another optional part of the apparatuscan include a vibrator or other non-objectionable indicator that isautomatically enabled instead of the objectionable audio sound, when thereceiver is in a restricted area. Further, the objectionable audiosignal may be reproduced or generated in the microcontroller's software.The muting operation can be implemented in software, rather than beingdone through a signal that is output from the microcontroller, as isillustrated herein. Or it can be implemented by a mechanical orelectro-mechanical coupling. While the invention has been described inconnection with an illustrative embodiment, obvious variations thereinwill be apparent to those skilled in the art without the exercise ofinvention, accordingly the invention should be limited only to the scopeof the appended claims.

While a particular embodiment of the invention has been shown anddescribed, it will be obvious to those skilled in the art that changesand modifications may be made therein without departing from theinvention in its broader aspects, and, therefore, the aim in theappended claims is to cover all such changes and modifications as fallwithin the true spirit and scope of the invention.

1. A system for restricting radio frequency transmissions of a cellulartelephone within a restricted area comprising: i) a restricted areawherein all radio transmissions are restricted, that restricted areabeing either a fixed-location contiguous physical space, or a movingvehicle's interior contiguous physical space, where a cellular telephonemight be operable; ii) a nonempty set of cellular telephones disposedwithin the restricted area, each cellular telephone including a radiofrequency transmitter for transmitting, and a radio frequency receiverfor receiving radiofrequency signals; iii) a radio frequencytransmissions inhibitor, the radio frequency transmissions inhibitorbeing capable of selectively disabling the radio frequency transmissionsof a first selected subset of the plurality of cellular telephones, thisselective disabling being directly responsive, at least in part, towhether or not the cellular telephone is in the restricted area; and iv)an emergency override, the emergency override capable of selectivelyenabling the radio frequency transmissions of a second selected subsetof the plurality of cellular telephones, wherein if a cellular telephoneis a member of the first selected subset and a member of the secondselected subset, the cellular telephone's radio frequency transmissionsare enabled.
 2. The system of claim 1, wherein the inhibitor, oremergency override, or both, communicate using i) a control-signaltransmitter disposed within the restricted area; ii) a control-signalreceiver disposed within the plurality of cellular telephones; and iii)a control signal generated by the transmitter and received by thereceiver, the signal either inhibiting or allowing radio frequencytransmissions from a subset of the plurality of cellular telephones. 3.The system of claim 2, wherein the control-signal receiver is separatefrom the radio frequency receiver.
 4. The system of claim 3, wherein thecontrol-signal receiver is selected from the group of an ultrasonicreceiver and an infrared receiver.
 5. The system of claim 2, wherein thecontrol-signal transmitter is selected from the group of an ultrasonictransmitter and an infrared transmitter.
 6. The system of claim 2,wherein the control-signal is received by all of the plurality ofcellular telephones, and wherein each of the plurality of cellulartelephones further comprises decoding circuitry for decoding an addressstored within the signal to determine whether the particular cellulartelephone is allowed to transmit radio frequency transmissions.
 7. Thesystem of claim 1, wherein the radio frequency transmissions inhibitoris disposed within the restricted area.
 8. The system of claim 1,wherein the restricted area has at least one entrance and wherein theradio frequency transmissions is disposed at the least one entrance. 9.The system of claim 1, wherein each of the plurality of cellulartelephones further comprises emergency override circuitry coupled to theradio-frequency receiver and the radio frequency transmitter, andwherein an emergency override command is received at least in part bythe radiofrequency receiver, and wherein the emergency overridecircuitry activates the radio frequency transmitter.
 10. A system forrestricting the ringing of a cellular telephone within a restricted areacomprising: i) a restricted area wherein ringing of all cellulartelephones disposed within the restricted area is muted, that restrictedarea being either a fixed-location contiguous physical space, or amoving vehicle's interior contiguous physical space, where a cellulartelephone might be operable; ii) a a nonempty set of cellular telephonesdisposed within the restricted area, each cellular telephone including aradio frequency receiver for receiving radio-frequency signals and aringer; iii) a ring inhibitor, the ring inhibitor capable of selectivelydisabling ringing in a first selected subset of the plurality ofcellular telephones, this selective disabling being directly responsive,at least in part, to whether or not the cellular telephone is in therestricted area; and iv) an emergency override, the emergency overridecapable of selectively enabling ringing of a second selected subset ofthe plurality of cellular telephones, wherein if a cellular telephone isa member of the first selected subset and a member of the secondselected subset, the cellular telephone's ringing is enabled.
 11. Thesystem of claim 10, wherein the ring inhibitor, emergency override, orboth, communicate using: i) a control-signal transmitter disposed withinthe restricted area; ii) a control-signal receiver disposed within theplurality of cellular telephones; and iii) a control signal generated bythe transmitter and received by the receiver, the signal eitherinhibiting or allowing ringing from a subset of the plurality ofcellular telephones.
 12. The system of claim 11, wherein thecontrol-signal receiver is separate from the radio frequency receiver.13. The system of claim 12, wherein the control-signal receiver isselected from the group of an ultrasonic receiver and an infraredreceiver.
 14. The system of claim 11, wherein the control-signaltransmitter is selected from the group of an ultrasonic transmitter andan infrared transmitter.
 15. The system of claim 11, wherein thecontrol-signal is received by all of the plurality of cellulartelephones, and wherein each of the plurality of cellular telephonesfurther comprises decoding circuitry for decoding an address storedwithin the signal to determine whether the particular cellular telephoneis allowed to ring.
 16. The system of claim 10, wherein the ringinhibitor is disposed within the restricted area.
 17. The system ofclaim 10, wherein the restricted area has at least one entrance andwherein the ring inhibitor is disposed at the least one entrance. 18.The system of claim 10, wherein each of the plurality of cellulartelephones further comprises emergency override circuitry coupled to theradio-frequency receiver and the ringer, and wherein an emergencyoverride command is received at least in part by the radio-frequencyreceiver, and wherein the emergency override circuitry activates theringer.